The development of surfactant-templated mesostructures represents a major advance in materials chemistry. Several attractive features, such as large surface areas, tunable pore sizes and volumes, and well-defined surface properties make mesostructured materials ideal for hosting molecules of various sizes, shapes, and functionalities. For example see Stein, A., et al., Adv. Mater. 2000, 12, 1403-1419; and Sayari, A., et al., Chem. Mater. 2001, 13, 3151-3168. Hexagonally ordered mesoporous silicate structures were discovered by Mobil Corp. (M41S materials like MCM-41) and by Kuroda, et al., (FSM-16 materials). See, e.g., Kresge, C. T., et al., Nature 359, 710 (1992) and Yanagisawa, T. et al., Bull. Chem. Soc. Jpn. 63, 988 (1990). Structures of uniform pore sizes can now be formed throughout the mesopore size range, which encompasses 2-50 nm by IUPAC definition. See, Sing, et al., Pure Appl. Chem. 57, 603 (1985).
In the field of drug delivery, many site-selective deliveries, e.g., deliveries of highly toxic antitumor drugs, such as Taxol, require “zero release” before reaching the targeted cells or tissues. Unfortunately, the release of compounds from many drug delivery systems takes place immediately upon dispersion of the drug/carrier composites in water. For example, see Radin, S., et al., J. Biomed. Mater. Res. 2001, 57, 313-320; Aughenbaugh, W., et al., J. Biomed. Mater. Res. 2001, 57, 321-326; and Kortesuo, P., et al., Int. J. Pharm. 2000, 200, 223-229. The release mechanism of other systems, such as biodegradable polymer-based drug delivery systems, also relies on the hydrolysis-induced erosion of the carrier structure. See Uhrich, K. E., et al., Chem. Rev. 1999, 99, 3181-3198; and Langer, R. Acc. Chem. Res. 1993, 26, 537-542. Additionally, many polymeric based release systems require organic solvents for drug loading, which can trigger undesirable modifications of the structure or function of the encapsulated molecules, such as protein denaturation or aggregation. See Li, Y.; Kissel, T., J. Controlled Release 1993, 27, 247-257.
The development of mesoporous silica-based carrier systems for controlled-release delivery of drugs, biocides, genes, or even proteins in vitro or in vivo is of keen interest. See Vallet-Regi, M., et al., Chem. Mater. 2001, 13, 308-311; Munoz, B., et al., Chem. Mater. 2003, 15, 500-503; Ramila, A., et al., J. Sol.-Gel Sci. Technol. 2003, 26, 1199-1202; Diaz, J. F., et al., J. Mol. Catal. B: Enzym. 1996, 2, 115-126; Han, Y.-J., et al., J. Am. Chem. Soc. 1999, 121, 9897-9898; Kisler, J. M., et al., Microporous Mesoporous Mater. 2001, 44-45, 769-774; Yiu, H. H. P., et al., Microporous Mesoporous Mater. 2001, 44-45, 763-768; and Takahashi, H., et al., Microporous Mesoporous Mater. 2001, 44-45, 755-762. Despite this current interest, there remains a need for novel carrier systems that can be used for the controlled-release delivery of drugs, biocides, genes, or proteins in vitro or in vivo.